This invention relates to a method of water heater fabrication and a water heater construction resulting therefrom and more particularly to a novel method of foam insulating a water heater.
Water heaters are manufactured and used in large numbers throughout the world. Water heaters often comprise a cylindrical tank containing a body of water, a cold water inlet, a hot water outlet, a body of insulation surrounding the tank and a mechanism for heating the body of water contained within the tank. Many water heaters heat the body of water contained within the tank by means of electrical heating elements penetrating the tank through its cylindrical side wall. Since the heating elements sometimes fail before the expiration of the useful life of the water heater, the heating elements are often removably mounted in the tank. A thermostat is often mounted on the tank adjacent the heating elements and controls the flow of electric current to the heating elements.
Recently, insulation of water heaters has taken the form of foam insulation surrounding the tank, which is in turn surrounded by a sheet metal jacket. The foam insulation is created in place by introducing foam forming materials into the volume defined by the exterior of the tank and the interior of the sheet metal jacket and allowing this material to form foam and fill the volume. In this method of manufacturing a water heater, steps must be taken to prevent the foam material from penetrating into areas from which it must be excluded. One method of performing this task is described in Denton 4,527,543 and uses a plastic film envelope to contain the body of foaming materials in selected areas. Insulation around the entry points for electric heating elements and the like is achieved through use of flexible fiberglass or a pre-molded rigid polyurethane foam insulation body protected by the envelope. This method uses a large plastic envelope which must be manufactured for each water heater positioning the envelope within the water heater prior to introducing the foam and introducing the foaming forming materials into the envelope only. An inventory of envelopes is required. An additional step in fabrication of the water heater is required and wastage in the form of torn envelopes and the like created in the manufacturing process may result.
Other methods using flexible sealing materials have also been attempted. These methods, generally, require additional parts which must be in inventory and often require extra manufacturing steps.